Antenna circuit matching the soil conditions

ABSTRACT

A wireless sub-surface soil sensor having a tunable antenna that can be optimized for transmission through various soils is disclosed herein. The wireless sub-surface sensor preferably also measures the moisture and salinity of a material. The wireless sub-surface sensor preferably includes a cover for protecting circuitry of the sensor. The wireless soil sensor is designed to be buried underground and to transmit to above ground receivers.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional PatentApplication No. 61/149,692, filed on Feb. 2, 2009, which is herebyincorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to antenna for a wireless sub-surfacesensor.

2. Description of the Related Art

The prior art discusses other irrigation systems and methods.

Closing an underground to above ground RF communication link is achallenging task. The challenge is typically due to difficultpropagation conditions perpetrated by high water content as well as highconductivity in the soil.

The moisture and conductivity vary over time depending on environmentalstimulus. High water content increases the rate of absorption of RFenergy. Salinity and moisture both change the die-electric constant ofthe soil, effectively detuning the antenna element as water contentchanges over time.

In instances, it is possible to adaptively modify the antenna tuningelements, to attempt to tune the antenna to the current state of thesoil.

However, in some instances it may not be possible to overcome theadverse effects of moisture in the ground by direct tuning of the RF andantenna components on board the underground wireless sensor. In otherinstances, certain wireless sensing devices may not be able to adapttheir tuning in close to real time to match the soil conditions.

The Present Invention seeks to resolve the problems of the prior art.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a solution to the problems of the priorart. The inventors of the present invention noticed the dielectric ofsoil, and how it changes with moisture and salinity, which led them tobelieve that a radiofrequency (“RF”) antenna of a wireless sub-surfacesoil sensor may be able to be tuned based on moisture and salinitymeasurements. The inventors measured soil moisture and salinity usingnovel sensors which also provided the electrical properties of the soilin which the wireless sub-surface soil sensor was placed. Theseelectrical properties affect the efficient transmission and range of anantenna. The inventors realized that an antenna could be configured tooptimize transmission efficiency and boost range. Components added tothe antenna circuitry controlled by the processor allow for the antennato be tuned based on the electrical properties of the soil.

RF impedances (complex resistances) are often characterized on a twodimensional SMITH® Chart. A discussion of SMITH® Charts is set forth inDesigning Impedance Matching Networks With the HP 8751A, Hewlett-PackardCompany, 1990, which is hereby incorporated by reference in itsentirety. Another discussion of SMITH® Charts is set forth in Stephen DStearns, Mysteries of the Smith Chart, Pacificon 2001, 2001, which ishereby incorporated by reference in its entirety. The inventors noticedthat if the antenna is tuned in a specific and novel manner, itsimpedance is shifted in an arc around the ideal match (about 50 ohms) asmoisture levels in the soil changed. By characterizing the arc by aradius and angle, the inventors were able to tune the radius to remainnearly constant. Only the phase angle of the impedance changed. Theinventors designed the physical antenna structure, board structure,housing (air space) and tuning elements to maintain a constant impedancemagnitude. This became an automatic, adaptive RF tuning which improvedantenna performance across a range of soil moisture levels.

One aspect of the present invention is a wireless soil sensor comprisinga microcontroller, an antenna, and an antenna circuit. The antennacircuit is in communication with the microcontroller. The antennacircuit preferably comprises means for utilizing a real-time soilconductivity value of a soil area and a real-time soil dielectricconstant value of a soil area to vary the properties of the antenna toclosely match the soil conditions and improve a communication range andcommunication reliability of the antenna.

The wireless soil sensor further comprises a soil moisture circuit and asoil salinity circuit. The microcontroller is preferably configured tomeasure analog voltages and perform calculations to determine thereal-time soil conductivity value and the real-time soil dielectricconstant value. The antenna circuit preferably comprises a plurality ofresistors and inductors for tuning the antenna.

Another aspect of the present invention is a wireless soil sensorcomprising a microcontroller, an antenna, a probe conducting structure,a soil moisture circuit, a soil salinity circuit and an antenna circuit.The probe conducting structure is preferably placed in the materialforming a capacitor connected to the soil moisture circuit. The soilmoisture circuit preferably comprises a high frequency oscillator forapplying electrical stimulus to the probe structure, a known referencecapacitor connected in series to the high frequency oscillator, and afirst voltage meter located between the high frequency oscillator andthe reference capacitor. The soil salinity circuit preferably comprisesa low frequency oscillator for applying electrical stimulus to the probestructure, a known reference resistor connected in series to the lowfrequency oscillator, and a second voltage meter located between the lowfrequency oscillator and the reference resistor. The respective circuitsconnect between the reference capacitor and the reference resistor, atwhich point the circuits are connected to the probe structure and athird voltage meter. The antenna circuit is in communication with themicrocontroller. The antenna circuit preferably comprises means forutilizing a real-time soil conductivity value of a soil area and areal-time soil dielectric constant value of a soil area to vary theproperties of the antenna to closely match the soil conditions andimprove a communication range and communication reliability of theantenna.

The microcontroller is preferably configured to measure analog voltagesand perform calculations to determine the real-time soil conductivityvalue and the real-time soil dielectric constant value. The antennapreferably transmits at 2.4 GigaHertz.

Another aspect of the present invention is a method for tuning anantenna of a wireless sub-surface sensor positioned in a soil area. Themethod includes determining at least one real-time electrical propertyof a soil area. The method also includes analyzing the at least onereal-time electrical property to determine an optimal antenna propertyfor efficient transmission and range. The method also includes tuning anantenna of a wireless sub-surface sensor to the optimal antenna propertyfor efficient transmission and range to create a tuned antenna. Themethod also includes transmitting data from the tuned antenna to areceiver above ground.

Another aspect of the present invention is a wireless soil sensor. Thewireless soil sensor is preferably capable of measuring soil moisture,soil salinity and soil temperature, while buried beneath the surface andalso capable of wirelessly transmitting the measurements to a receiverabove the surface for eventual transmission to an engine forcalculations and other outputs.

The wireless soil sensor preferably has a tine sleeve for placement overa portion of the sensor. The sleeve is removed when the sensor is readyto be buried beneath the surface of the soil.

The sensor preferably links to a controller, is preferably associatedwith a watering zone which is to be controlled by a controller. At leasta portion of the sensor is preferably waterproof. The tine sleevepreferably has a small patch of exposed PCB conductor which is connectedto another, which allows the sensor to assume it is in a hibernationstate (for power savings, suppressed communications and suppressedemissions). Essentially, while the sensor has the tine sleeve attached,it is in an inactive state.

The tine sleeve further protects the sensitive components of the sensorduring shipment.

Removal of the tine sleeve is an intuitive indication that the sensor isto be associated and buried. The sensor assumes a period of activecommunication so that a controller/interrupter can learn of its presenceand prompt assignment to a watering zone or zones.

After a set period of time, the sensor preferably assumes a normalsensing and broadcast mode. The tine sleeve further acts a physicalreceipt, allowing for marking with the date, position of installationand corresponding watering zones. The tine sleeve further provides thefunction of enabling safe transportation of the end-of-life or returnfor repair of the sensor to a factory or alternative site.

The wireless sensor preferably infers moisture and salinity levels bymeasuring the dielectric constant of the surrounding soil. A radioantenna used to relay these measurements to a central controller isaffected (de-tuned) by surrounding changes in the dielectric constant.The present invention can adaptively tune the antenna impedance matchvia RF switches and passive components based on moisture and salinityreadings. This increases the communication range and reduces powerconsumption.

A user interface for an irrigation interrupter preferably has a defaultdisplay of 128 by 64 pixel. In a limited space, the display communicatesa tremendous amount of information in an extremely intuitive way. Sixcolumns for watering zones are used in the display. Each zone shows amoisture assessment of Ok, Wet, Dry, or Cold. Next to this is a visualindication of the moisture level in the zone, as reported by one or moresensors, adapted to a soil/plant type. A bar showing moisture levelpreferably has two marks indicating a lower level where no wateringwould be interrupted, an upper level indicating that all watering wouldbe interrupted, and in the zone in between, a sensor for how much of thenormal watering period will be allowed before a mid-flow cutoffattenuates watering. A bold OFF and ON indication blinks between theview and the underlying moisture status normally shown. The blinkingbehavior is set to occur when a zone input is active, and indicates theaction being taken by the interrupter. Above the moisture indications isa row showing the control status of each zone-whether it is controlledby one or more sensors, or has been placed in manual ON or manual OFF.The user interface allows for determination of a manual mode with only acasual view of the user interface. The top line shows the system status(Auto, Bypass, Master, Slave) and the recent average of water saving,calculated by the percentage of time normally watering has beenattenuated. Master and Slave are used to enable “chaining” of multipleinterrupters together to control additional zones, preferably six at atime. At the bottom of the display, icons show whether one or more thanone sensor is assigned per zone. A solid square is a sensor with noperformance issues. A hollow square indicates low battery. A triangleindicates RF reception issues. A hollow triangle represents RF receptionand battery issues.

In such conditions, where information about soil moisture and salinityconditions at the time of attempted transmission is available to thewireless sensor, for example when there are on board moisture andconductivity sensor present, the wireless transmitter will perform asimple computation to determine whether its transmission will besuccessful given the network activity history and the soil moisture andconductivity levels. The wireless sensor will track the moisture andconductivity levels, and based on those levels will adjust itstransmission attempts. The impact of this decision making is that itwill predict when the transmission will fail, and thus refrain fromtransmitting. This adaptive adjustment of the transmission schedule willhelp conservation battery life for battery operated sensor nodes. Thisadaptive schedule will be effective for one way as well as two waycommunication links. However its impact will be most evident for two-wayover the air protocols.

It is an object of the present invention to provide a proprietarywireless root zone intelligence system that measures real time soilmoisture, temperature and salinity. It is an object of the presentinvention to provide an advanced wireless sensor and analytical,intuitive, fully interactive software. It is an object of the presentinvention to optimize turf health and playability, improve productquality, optimize resource utilization.

Having briefly described the present invention, the above and furtherobjects, features and advantages thereof will be recognized by thoseskilled in the pertinent art from the following detailed description ofthe invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a top perspective view of a wireless soil sensor of thepresent invention with a sleeve attached over a portion of the wirelesssoil sensor.

FIG. 2 is a first side view of the wireless soil sensor of FIG. 1.

FIG. 3 is an opposing side view of the wireless soil sensor of FIG. 1.

FIG. 4 is top plan view of the wireless soil sensor of FIG. 1.

FIG. 5 is a top perspective view of a wireless soil sensor of thepresent invention without a sleeve attached over a portion of thewireless soil sensor.

FIG. 6 is a first side view of the wireless soil sensor of FIG. 5.

FIG. 7 is top plan view of the wireless soil sensor of FIG. 5.

FIG. 8 is a rear plan view of the wireless soil sensor of FIG. 5.

FIG. 9 is a schematic diagram of a preferred embodiment of a system ofthe present invention.

FIG. 9A is a schematic diagram of a preferred embodiment of a system ofthe present invention illustrating a mesh network established by thetransmitters of the system.

FIG. 9B is a schematic diagram of an embodiment of a sensor node of thesystem.

FIG. 9C is a schematic diagram of an embodiment of a sensor node of thesystem.

FIG. 10 is a flow chart of a preferred method for improving acommunication range and communication reliability of an antenna for awireless soil sensor buried below the surface of a land area.

FIG. 11 is an image of flushing information.

FIG. 12 is an image of indicators for the optimal zone.

FIG. 13 is an image of proactive irrigation practices.

FIG. 14-1 is a graph of soil temperature for a number of days todemonstrate that without an understanding of the overall conditions thetemperature data is a minimal value.

FIG. 14-2 is a graph of soil moisture for a number of days todemonstrate that without an understanding of the overall conditions thetemperature data is a minimal value.

FIG. 14-3 is a graph of soil salinity for a number of days todemonstrate that without an understanding of the overall conditions thetemperature data is a minimal value.

FIG. 14A-1 is a graph of soil temperature for a number of days todemonstrate the benefit of knowing the overall conditions and defining azone for optimum performance.

FIG. 14A-2 is a graph of soil moisture for a number of days todemonstrate the benefit of knowing the overall conditions and defining azone for optimum performance.

FIG. 14B is a graph of soil salinity for a number of days to demonstratethe benefit of knowing the overall conditions and defining a zone foroptimum performance.

FIG. 14C-1 is a graph of soil salinity for a number of days todemonstrate good quality irrigation.

FIG. 14C-2 is a graph of soil salinity for a number of days todemonstrate poor quality irrigation.

FIG. 15 is a schematic diagram of a prior art irrigation control system.

FIG. 16 is a schematic diagram of an irrigation control system with anirrigation interrupt.

FIG. 17 is a schematic diagram of an irrigation control system with awireless irrigation controller.

FIG. 18 is a schematic diagram of a prior art irrigation control system.

FIG. 19 is a schematic diagram of an irrigation control system with atethered sensor.

FIG. 20 is a schematic diagram of an irrigation control system with awireless interrupt.

FIG. 21 is a schematic diagram of an irrigation control system with awireless controller.

FIG. 22 is a block diagram of an alternative embodiment of a sensor.

FIG. 23 is a graph of a calibration curve showing variation in 1/RC withincreasing sample conductivity.

FIG. 24 is a schematic diagram of an embodiment of a sensor.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is preferably used with a system and method suchas disclosed in Glancy, et al., U.S. Patent Publication Number2006/0178847 for an Apparatus And Method For Wireless Real TimeMeasurement And Control Of Soil And Turf Conditions, which is herebyincorporated by reference in its entirety.

The present invention may be used with a system, sensor and method suchas disclosed in Campbell, U.S. Pat. No. 7,482,820 for a Sensor ForMeasuring Moisture And Salinity, which is hereby incorporated byreference in its entirety. The present invention may use a chemicalsensor probe such as disclose in U.S. Pat. No. 4,059,499 which is herebyincorporated by reference in its entirety. The present invention may usea chemical sensor probe such as disclose in U.S. Pat. No. 5,033,397which is hereby incorporated by reference in its entirety. Systems andmethods for optimizing irrigation are disclosed in Magro et al., U.S.patent application Ser. No. 12/697,226, filed on Jan. 30, 2010, for aMethod And System For Monitoring Soil And Water Resources, which ishereby incorporated by reference in its entirety. Systems, methods,sensors, controllers and interrupters for optimizing irrigation aredisclosed in Campbell et al., U.S. patent application Ser. No.12/697,254, filed on Jan. 31, 2010, for a Method And System For Soil AndWater Resources, which is hereby incorporated by reference in itsentirety.

A wireless sub-surface sensor 21 is shown in FIGS. 1-8. The wirelesssub-surface sensor is placed in the soil below the surface to monitorvarious parameters of the soil such as electrical properties. Otherparameters include moisture, salinity and temperature.

As shown in FIGS. 9, 9A and 9B, a preferred embodiment of a system ofthe present invention is generally designated 20. The system preferablyincludes a plurality of wireless sub-surface sensors 21 (upper soil 21 aand lower soil 21 b), a plurality of above-ground receivers 22, acontrol engine located at an operations center, and a plurality ofabove-ground sensors 24. The above ground sensors 24 preferably measuresair temperature, wind speed, and relative humidity.

FIG. 9B illustrates a wireless sub-surface sensor 21 preferably utilizedin the system 20. The wireless sub-surface sensor 21 preferably has ahousing 30, a processor 31, a configuration switchable antenna 32,sensors 33 a, 33 b and 33 c, and a power supply 34. The sensors 33 arepreferably measure the electrical properties of the soil.

FIG. 9C illustrates a wireless sub-surface sensor 21 alternativelyutilized in the system 20. The wireless sub-surface sensor 21 preferablyhas a housing 30, a processor 31 with an integrated sensor 33, aconfiguration switchable antenna 32, and a power supply 34.

FIG. 10 is a flow chart of a preferred method 1000 for improving acommunication range and communication reliability of an antenna for awireless soil sensor buried below the surface of a land area. At block1001, a wireless sensor is activated. At block 1002, a plurality of soilelectrical properties for the land area are measured by the wirelesssub-surface sensors. At block 1003, data from the wireless sensor istransmitted to at least one receiver above the surface of the land areaat a plurality of switchable antenna configurations. More specifically,the wireless sub-surface sensor transmits data at a first antennaconfiguration, then switches to a second antenna configuration and againtransmits the data to the receiver. The wireless sub-surface sensorcontinues to switch antenna configurations and transmit data to thereceiver. At block 1004, the receiver and control engine, monitor asignal property of each transmission of data for each of the pluralityof switchable antenna configurations. At block 1005, the above steps arerepeated every predetermined number of sensor transmission cycle, whichis preferably sixty. At block 1006, a map of the signal property for theplurality of switchable antennal configurations is created by aprocessor preferably located at the control engine. The map is providedto each of a plurality of wireless sub-surface sensors. At block 1007,the most favorable antenna configuration for the position of thewireless sub-surface sensor is determined from the map. At block 1008,the wireless sub-surface sensor configures the antenna to the mostfavorable antenna configuration. At block 1009, data from the wirelesssub-surface sensor is transmitted to the receiver at the most favorableantenna configuration for that wireless sub-surface sensor.

An example of a protocol that will implement an embodiment of thisapproach is provided below. It is provided in the context of a two wayover the air link, but can easily be applied to a one way link.

A wireless device (soil sensor 21, interrupter 12 or controller 11)typically goes through a network entry process, in which it searches forand locks onto the signals of other members of the wireless network itis entering. After the signal lock, a handshake takes place, where theentering node transmits and expects to receive a sequence of welldefined messages over the air. At the conclusion of this handshake, theentering node is considered a member of the network. It will be able totransmit and receive over the air messages using a well definedprotocol. It will be considered a “Joined” member. A “joined” member maymaintain a connection oriented or a connection less link with its radioneighbors. (Example of a connection oriented link is a time synchronizedCDMA channel between a station and a cell tower. Example of aconnection-less link is the Carrier Sense Medium Access (CSMA) linkbetween a WiFi station and its Access Point).

Typically, if the “joined” member is not able to communicate with theother end of the link within a predefined window, it loses its “joined”status, and has to go through a network entry process again. At theleast, it may have to perform a less complex re-synchronization task tore-establish its time synch with the network (if is uses a connectionoriented link). The link establishment, re-synch, or network entryprocess will continue (typically with less and less frequency, uponfailed attempts) until a) the node rejoins the network, b) the timeinterval between reentry attempts becomes so large that the nodeeffectively becomes dormant, or c) until the node runs out of battery.

The wireless soil sensor 21 is required to transmit messages for all ofthe above transactions. If the cause of loss of “joined” status is duesto surrounding soil that is too moist or too saline then the rejoinattempts will also fail. If this condition is not detected, the wirelesssoil sensor 21 will continue wasting scarce battery reserves fortransmissions. The adaptive transmission scheduling mechanism discussedhere takes into account the moisture and conductivity of the soil thatsurrounds the wireless soil sensor 21. It will stop transmissions untilthe moisture levels of the soil surrounding the node have dropped tomanageable levels that will allow successful transmissions.

An example of a preferred method of adaptive transmission is as follows.A preferred method for an adaptive transmission aspect of the presentinvention begins with determining if (x) number of consecutiveconnection attempts (or transmission) have failed. Next, the methodincludes determining if the measured moisture level (or a compositemetric that includes moisture and conductivity levels) is at somethreshold (y) or above. Next, the method includes assuming thesurrounding soil is too wet. Next, the method includes suspending thetimers that control the transmission activity of the node. Next, themethod includes, continuing to sample the moisture levels, and as longas the moisture levels are above threshold (z), attempting to connectonce every predetermined time period, T (T time units only, where T islarger than typical inter-transmission intervals). Next, the methodincludes determining when the moisture levels have dropped below athreshold (w), then un-suspending the timers and a state machine thatcontrols transmissions. Next, the method includes, allowing the normalprotocol to resume for the system.

One can manage what one can measure. And, one can do it all on a realtime basis. Soil intelligence equals savings and health. The presentinvention is preferably a complete package of advanced software,agronomic services and wireless sensor system that helps take theguesswork out of turf management. The present invention turns raw datainto useful operating thresholds that help maintain and optimize planthealth and performance. The present invention provides the necessaryformula that automatically alerts when and where a facility might beexperiencing stress and what the treatment options are.

One aspect of the present invention has a data collection component ofthe software, which allows for monitoring in real time, from an officeor from on-site or remote locations, the key variables of moisture,salinity and temperature from each sensor site. The graphic displays areuser-friendly and the present invention helps set high-low thresholdranges for each sensor location so that one instantly knows whether thesoil is in or out of the optimal range for growth conditions andplayability. By continuously analyzing the recorded data and thresholdsfor each location, this component visually alerts one to conditions ateach sensor location and suggests what actions are needed to be moreefficient and effective.

One aspect of the present invention optimizes turf and crop health andplayability by measuring root zone moisture, salinity and temperatureand applying best practices to your turf management. Once the wirelesssoil sensors 21 are in the ground sending raw data, an optimal zone isdevised by analyzing accumulated sensor data, putting decades ofagronomic experience to use and applying tested scientific principles.The Zone defines the upper and lower operating thresholds to ensureplant health. This helps with: course evaluation; soil and wateranalyses; review of existing practices including irrigation, nutritionalinputs and maintenance; threshold determinations; sensor placement andmore. On a real-time basis, one can manage greens, tees, fairways andrough to keep a facility in prime condition.

The wireless soil sensor 21 provides wireless interface between thesensing elements and the Communication Control Nodes (CCNs) thatpreferably form a mesh network. The key features include the shape: 8×4inches. Buried with a Standard Cup Cutter. Supports sensors: analog ordigital. 3 “D” Cell batteries: 4+ years life, field replaceable. 1 WattFHSS radio board supports approximately 400 ft. range 4 in. in ground.Sensor interface and antenna for over air programming for productupgrades.

The key functionalities of the wireless soil sensor 21 are as follows:provide accurate, real-time data on soil moisture, temperature andsalinity. Key Features: Pre calibrated for sand, silt and clay. Moisturemeasurement. Accuracy: +/−0.02 WFV from 0 to saturation at <2.5 dS/mconductivity. +/−0.04 WFV from 0 to saturation at 2.5-5 dS/mconductivity. Repeatability: +/−0.001 WFV. WFV is the fraction of soiloccupied by water, a soil at 10% soil moisture has a WFV of 0.10.Conductivity measurement: Accuracy: +/−2% or 0.02 dS/m, whichever isgreater, 0-2.5 dS/m.+/−5%, 2.5-5 dS/m. Repeatability: +/−1% or 0.01 dS/mwhichever is greater, 0-2.5 dS/m.+/−4%, 2.5-5 dS/m. Temperaturemeasurement: Accuracy: +/−0.5° C. from −10 to +50° C., +/−1° F. from 14to 122° F. Repeatability: 0.05° C., 0.1° F. Benefits: Dual sensors allowgradients of soil moisture, conductivity, and temperature to bemonitored. High accuracy and repeatability. No individual sensorcalibration required.

Above-Ground Wireless Mesh Network: Communication Control Nodes. KeyFunctionality: CCNs are the interface to the Sensor Nodes. Each is aradio node that automatically joins and forms the mesh network on powerup. Key Features: Range of ˜1 mile above ground unobstructed. Requires 1Amp while transmitting. 12-24 Volt AC or DC power. Can be attached via110/220 Volt power adapter. Weather proof enclosure. Benefits: Selfforming, self healing, multihop mesh network; No special wiringrequired; Two way communications with link quality statistics; Controlof buried nodes; The multihop mesh allows extension of the wirelesscoverage area far beyond the nominal range of the radios.

Agronomy. Soil health impacts everything grown above. What is agronomy?It is the study of plant and soil sciences and how they impact crop andplant production, performance and yield. Every plant has specifictolerances to environmental variables like moisture, temperature andsalinity which impact the ability to grow, flourish, proliferate andperform to expectations. Agronomists using the present invention helpdefine those optimal threshold levels as well as their impacts on root,leaf and lateral growth, responses to man-made or natural environmentalstress, and resistance to disease and insect pressure. As a result, inthis case water usage was reduced by nearly 30% while playability wasenhanced uniformly. The indicator of the present invention predicts thelikelihood for disease outbreaks before they happen.

The software package utilized feeds off data provided by the wirelesssoil sensors 21 and wireless communications system. It displays realtime conditions and provides comprehensive intelligence and predictiveactions. The system helps establish health- and performance-optimizingoperating threshold ranges, evaluate your data and current practices,and refine existing programs. The results, optimal turf conditions andreal savings, will generate a strong and lasting return on investment.The agronomic benefits include more efficient salinity management,uniform irrigation, deeper rooting, predictive disease control andhealthier, more stable conditions. There are environmental benefits aswell like water conservation, reduced use of phosphates, nitrates andpesticides, a reduced carbon/water footprint and regulatory compliance.

Real time sensor measurements using the present invention also includesoil oxygen, pH, concentrations of specific ion species—(Na+ has a verydetrimental effect compared to the same concentration of Ca+2).Pollutant measurements include both hydrocarbons (oils, gasoline, etc.)and metals (chromium, lead, etc.).

As to the wireless transmission network, an alternative process of anadaptive model may be utilized with the present invention. An antenna,designed for efficient RF communication in air is relativelystraightforward because the key electrical properties of thetransmission medium (air) are well known and essentially constant. Inbelow ground RF transmission, the key properties of the soils varygreatly with moisture content and salinity hence it is a much moredifficult problem to design an efficient antenna. In addition, the bestantenna design is influenced by how deeply buried the antenna is. Thepresent invention includes elements to the antenna circuit that, undercontrol of microcontroller, allow for varying the properties of theantenna to more closely match the conditions and improve range andreliability of communication. The wireless sub-surface sensor 21measures both the dielectric constant of the soil (moisture) andconductivity (salinity) directly. Hence, the sensor measures preciselythe two most important factors affecting antenna efficiency.

In a predictive model, the method includes activating a sensor andmeasuring soil electrical properties. The method also includes, based onthe soil properties, activating antenna elements to give an effectivetransmission. The method also includes transmitting sensor data.

In an adaptive model, the method includes activating a sensor andmeasuring soil electrical properties. The method also includestransmitting data repeatedly until all switchable antenna configurationshave been attempted. The method also includes monitoring signal strengthfor each transmission. The method also includes repeat this processpossibly every 60 sensor transmissions.

As time progress, a receiver can put together a two dimensional map(soil dielectric constant on one axis, soil conductivity on the other)with received power for all antenna configurations. The map isdownloaded on some regular schedule to the buried sensor node. When thewireless sub-surface sensor 21 makes a measurement, the sensor reviewsthe map for the antenna configuration that gives the highest receivedsignal power at the receiver for the current conditions. A nodeconfigures an antenna and sends a packet of data. Even after the map isdownloaded, every 60 sensor readings preferably have all of thedifferent antenna configurations attempted which allows the map toevolve.

The advantage of this adaptive process is that it can make an allowancefor the actual depth of burial as well as the relative antenna locationsand orientations. This is important because different antennaconfigurations have different radiation patterns. Hence, it is possiblethat a less than ideal antenna configuration works best in that it hasthe highest radiated power in the particular direction and polarizationthat the receiver antenna lies in.

As shown in FIG. 15, an irrigation system 10′ includes a 24 VAC powersupply, a controller 11, and a valve box 13 with valves 123 a and 13 b.These irrigation systems 10′ work by using a 24 volt alternating currentsource to open valves 13 a and 13 b. When no current flows (open switch51), the valves 13 a and 13 b are closed and no water flows. Acontroller/timer 11 is used to turn on the current to the separatevalves 13 a and 13 b. Usually there is a “common” wire 53 that returnsthe current from all valves 13 a and 13 b. Separate “hot” wires 52 a and52 b are used for each of the valves 13 a and 13 b. As shown in FIG. 18,the irrigation controller 11 controls the valve box 13 through wires 17a and 17 b to provide water form source pipe 16 b to sprinkler pipe 16 afor dispersion on a soil 15 through sprinkler 14.

As shown in FIG. 19, the prior art is improved upon by a system 10 witha tethered sensor 21′ in which is a sensor coupled to an interrupter 12wired into the wirings 17 a, 17 b, 17 c and 17 d of the valve box 13.The interrupter 12 acts to turn off a scheduled irrigation if themoisture exceeds a predetermined threshold established by a user. Theinterrupter 12 acts as an in-line switch that closes (allowing currentto flow and the valve 13 to open) only if the controller 11 starts ascheduled irrigation and the soil moisture is below a predeterminedthreshold established by a user). In the system 10 of FIG. 19, theinterrupter 12 can only interrupt a scheduled irrigation, not initiatean irrigation. The system 10 has a sensor 21 which is cabled (nowireless communication). The system 10 of FIG. 19 has the advantage ofbeing very simple, it is capable of being easily installed intovirtually all existing irrigation systems, and it requires noindependent power (the system 10 draws power off the 24 VAC irrigationline).

As shown in FIG. 20, a wireless interrupt approach is similar to the“Tethered Sensor” system 10 of FIG. 19, except that wirelesscommunication is used between a wireless soil sensor 21 and aninterrupter 12. The wireless soil sensor 21 requires battery power andthe interrupter 12 requires a battery to accommodate flexible wirelessreporting. The principle advantage of the system 10 of FIG. 20 is thatno cabling is needed, and installation is simpler than the tetheredsystem 10 of FIG. 19. As shown in FIG. 20, the wireless soil sensor 21transmits a wireless signal 18 a to the interrupter 12 pertaining to themoisture levels of the soil in a particular soil area.

A wireless controller system 10 is shown in FIG. 21. The wirelesscontroller system 10 uses a wireless link back to a wireless irrigationcontroller 11 (there is no “interrupter”) The principle advantage of thewireless controller system 10 of FIG. 21 is that the wireless soilsensors 21 preferably initiate irrigation if needed (allowing for theuser to set scheduled irrigation times as well if desired). A user alsomay allow the wireless controller 11 to look at more than one wirelesssoil sensor 21 for each irrigation zone (area irrigated by one valve 13)taking an average, use the lowest value, etc. One can also allow forsimpler level adjusting, including such features as a “hot day” buttonnudging the target water levels up a notch and many others.

The goal of one aspect of the present invention is to develop aninexpensive and easy to install system compatible with existingirrigation systems that can be quickly configured byhomeowners/landscapers of limited technical sophistication. An objectiveof the present invention is an overall lower cost, a system that is easyto install in existing and new irrigation systems, setup that is as easyto use as a traditional irrigation controller, and careful design ofsetup features, default modes, user input device and display to give asuperior customer interface.

Irrigation interrupt of the system interfaces simply with existingirrigation control systems to over-ride scheduled irrigation whenmoisture levels hit user settable thresholds. When operating in thismanner, the system is incapable of initiating an irrigation event andneeds to be used with a conventional irrigation controller. Anirrigation controller 11 of the system 10 can initiate and stopirrigation events and replaces existing installation irrigationcontrollers or is suitable for complete control of new installationsthrough both timing of irrigation to certain times of the day as well asbased on near real-time soil moisture data.

As mentioned above, a typical irrigation controller system 10′ is shownin FIG. 15. The system 10′ includes a 24 VAC power supply connected to120 VAC and an irrigation controller 11. Wiring 52 a and 52 b leads fromthe controller 11 to one or more valve boxes 13. When the current loopis closed, the valves 13 a and 13 b open and a zone is watered.Typically, the controller 11 is set to turn on and off valves atpredetermined times for a set time.

In the irrigation interrupt system 10, as shown in FIG. 16, theinterrupter 12 is positioned between the standard irrigation controller11 and the valves 13 a and 13 b. A wireless soil sensor 21 is placed ineach irrigation zone and the wireless soil sensor 21 is in periodiccommunication with the irrigation controller 12. In this system,watering only occurs when both the standard irrigation controller 11indicates that it is time to water and the irrigation interrupter 12indicates that soil moisture is below a predetermined threshold. Theinterrupter 12 opens switch 54 a and 54 b to terminate the current flowthrough lines 52 a′ and 52 b′ and close the valves 13 a and 13 b. Line55 provides power to the interrupter 12, especially when the switch 51of the controller 11 is open.

In the wireless irrigation controller system 10 of FIG. 17, the sameinterrupter hardware is used but the inputs to the irrigationinterrupter 12 are always on, i.e. the irrigation interrupt 12 is now incontrol and irrigation will occur under the direct control of thewireless interrupter 12 based on soil moisture data. Different firmwareis necessary, but the hardware is identical with only minimal changes inthe wiring.

In both systems, power for the irrigation interrupter 12 is drawndirectly off the 24 VAC eliminating the need for a separate powersupply.

The system 10 is capable of operating with soil moisture only wirelesssoil sensors 21 with integrated two-way wireless telemetry, sensorfirmware, an irrigation interrupter/controller (Controller) andcontroller firmware. The wireless soil sensors consist of a soilmoisture only sensor, wireless two-way telemetry, microcontroller, andat least some non-volatile memory, and are preferably battery powered.These components are integrated into one physical package (no cabling)and the wireless soil sensor 21 is buried in strategic locations tomonitor soil moisture conditions. The sensor firmware manages makingsensor measurements, transmitting them to the controller, receivingcontroller commands, and power-management (putting system to sleep). Thecontroller 11 preferably consists of two-way wireless telemetrycompatible with the wireless soil sensors 21, a microcontroller,non-volatile memory, a user input (preferably a four or five way wheel),display (preferably 36 character two line LCD), and circuitry foropening or closing switches for irrigation zones (switch in an openposition is over-riding irrigation). In existing irrigation systems andfor use with an already installed controller, the wireless controller 11is spliced into existing wiring close to an existing irrigationcontroller. In replacing an existing irrigation controller or in newinstallations, the wireless controller 11 is directly connected toirrigation zone wiring. The controller firmware allows collection ofwireless telemetry of soil moisture data, “commissioning” of newwireless soil sensors 21, i.e. associating a wireless soil sensor 21with an irrigation zone and an installation, setting irrigationthresholds, etc.

All of the components preferably operate over a temperature range of −20to 70° C. (with the exception of the display which is operable over 0 to50° C.) and are capable of storage over −20 to 70° C. All componentspreferably are Human Body Model ESD resistant but not lightningresistant. Wireless soil sensors 21 are preferably fully waterproofwhile the interrupters 12 preferably only have a low level ofsplash-proofing. For the purposes of determining battery shelf life inthe wireless soil sensors 21, a temperature under 40 C is assumed(temperature, depending on battery technology, can greatly impact selfdischarge rates).

Wireless telemetry range of approximately 100-200 feet is preferred. Therange is achieved at depths of up to 12 inches and in moderate clutter(vegetation, slight topography, through garage wall, etc.). A wirelesssoil sensor 21 is preferably installed at least as close as 3 inchesfrom soil surface for monitoring soil moisture in shallow rooting turf.The package of the wireless soil sensor is preferably no larger than2″×2″×8″ (ideally 1.5″×1.5″×6″). A bulky package is difficult to install(particularly at shallow depths), disrupt soil environment, and aturn-off to consumers. A non-volatile memory is preferred. Timekeepingis accurate to within +/−2% which allows the wireless soil sensors 21 towakeup at on a regular schedule, timing for I2C commands, as well asscheduling sensor “listen” windows for wireless receive modes.

The wireless soil sensor 21 is capable of receiving simple operationalparameters wirelessly from a controller 11 or an interrupter 12, whichallows the controller 11 or the interrupter 12 to set reportinginterval, selection of adaptive algorithms, etc.

A procedure for re-programming the wireless soil sensors 21 afterproduction is included in order to allow for changes encountered indebugging or upgrades. Alternatively, it can be through a programmingheader in the battery or by some other wireless programming option.

The wireless soil sensor 21 is preferably able to detect imminentbattery, to prevent the wireless soil sensors 21 from failing suddenlywith no warning or begin to operate intermittently reflecting batterytemperature and other variable as well as possibly giving corrupted datathat may result in incorrect irrigation decisions.

The sensor firmware is capable of executing and reading I2C commands.Analog sensor requires I2C commands to control oscillator and make A/Dmeasurements. I2C commands need to be executed sequentially according toa sloppy timing of about +/−3 mS over 100 mS. I2C can operate anywherefrom 20 to 200 KHz. The sensor firmware is able to perform simplecalculations like conversion of raw A/D values into soil moisture whichrequires simple functions-addition, subtraction, division, polynomialsbut no log, trig, etc. functions. The sensor firmware is capable ofgoing into a very low power mode between set measurement interval withroutines to wake up at end of interval which may range from 1-100 min.which is set in a non-volatile configuration file which can be modifiedby interrupt controller. After measurement is complete, soil moisturedata needs to be sent to interrupt controller 11.

The sensor firmware preferably has a static soil moisture mode. Anoperational mode that allows the wireless soil sensor 21 to wake up,measure soil moisture, and if a change in soil moisture from the lastwirelessly reported measurement does not exceed a settable threshold,return to a sleep mode without sending data. This threshold value, aswell as whether this feature is enabled, preferably resides in anon-volatile configuration file which can be modified by the interruptcontroller 11. The wireless soil sensor 21 preferably transmits a newreading once every six hours regardless of soil moisture changes toconfirm operation.

The wireless soil sensor 21 preferably has a default mode firmware uponpower restart for the sensor firmware, which allows a wireless soilsensor 21 to be commissioned, i.e. assigned to a specific irrigationinterrupter to allow for resolving sensors from a close neighborsresidence. In addition, commissioning must be flexible to allow for achange in assigned interrupt controller 11 in the future or ifcommissioning is lost.

A wireless soil sensor 21 is preferably capable of a listening mode in apower efficient manner for receiving changes to the configuration filewirelessly from the interrupt controller 11 with a maximum file size of100 bytes at least once a month without degrading three year sensorbattery life. The wireless soil sensor 21 preferably has the ability todownload full operating firmware.

On a regular schedule (about once every six hours) the wireless soilsensor 21 preferably provides in addition to the soil moisture value,diagnostics such as battery voltage, and raw measured values not toexceed an additional 25 bytes. This data is used to assess performanceand for diagnosis of bugs or sensor failure.

If the raw A/D values used to determine soil moisture data are out ofnormal ranges, the wireless soil sensor 21 preferably sends a “Bad Data”even if the computed soil moisture value appears reasonable. This helpsdetect failed wireless soil sensors 21 and prevent bad control actions.

The irrigation interrupter 12 is capable of turning on and off ACcurrent up to 700 mA continuously at 70 C for each irrigation zone froman AC voltage range of 16 to 34 volts with no more that 1V in dropacross switching circuitry. Switching circuitry is not damaged byinductive transients generated by turn off of valve solenoids.

Regardless of whether the interrupt controller 11 is allowing orblocking irrigation, the interrupt controller 11 can detect the presenceof an AC voltage (generated by irrigation controller 11 to initiate anirrigation). This feature allows for calculations of savings such as %of scheduled irrigation events that were canceled by system.

The hardware for the irrigation interrupter 12 is preferably resistantto moderate ESD and transients that may enter system through 24 VACtransformer in order to be reliable.

The interrupt controller 11 draws power directly from nominal 24 VACtransformer to avoid having to use a separate power supply with amaximum current draw of 100 mA. The interrupt controller 11 operatescorrectly with an AC input varying from 16 to 34 VAC to account for ACmains voltage of 84 to 130 VAC (typical specified level of AC power seenin a household) and variation in transformer output with load.

The interrupt controller 11 is capable of operating in typicalresidential systems which have between four and eight zones. Moresophisticated systems could be addressed by using multiple units.

The interrupt controller 11 is preferably capable of a log for the last30 days of soil moisture readings for eight zones at 10 minute intervalas well as whether an irrigation event is occurring, and whether it hasbeen interrupted at 1 minute intervals in non-volatile memory. The logis preferably structured so accurate date and time is available for datarecord. This feature is good for both debugging purposes but also inallowing the system to display to the user the amount of water savedthus justifying the product.

Firmware responds as gracefully as possible to problems. For instance,if soil moisture data is out of range or uC lockup (possibly detected bywatchdog circuit) irrigation proceeds according to the irrigationcontroller 11 (i.e. no interrupt). If an irrigation interrupter 12 isoperating as a wireless irrigation controller (no standard irrigationcontroller), the system 10 should default to no irrigation. Failuremodes give obvious indication of problems.

Ample code space is preferably reserved to allow for extensiveadditional features in the future. All user settable configurations arepreferably stored in non-volatile memory so as to allow for seamlessrecovery from lockup or loss of power. Preferably, a real time clock hasthe ability to keep time after power loss for up to 1 month.

The interrupter firmware is capable of generating a user water savingsreport for the last day, week, and month (i.e. percent of scheduledirrigation that was interrupted) by zone and as a whole for all eightzones as well as total run time per zone.

A process is developed to allow sensors upon installation or systemexpansion to be assigned to a particular irrigation zone for aparticular irrigation interrupter. The process needs to be flexibleenough to allow for replacement of failed wireless soil sensors 21 aswell. This allows the system 10 to be used with neighboringinstallations without confusion as well as assigning the right sensor tothe right zone.

A user sets, for each zone, the maximum soil moisture level that willterminate an irrigation event. There is also a settable hysteresis, Y,i.e. if during a single scheduled irrigation event the soil moisturerises about the threshold X and irrigation is stopped, it would notbegin again until level fell to X-Y. This prevents valves from turningon and off rapidly when approaching the threshold. When new irrigationevent occurs, the threshold defaults back to X.

A hold feature allows a user to hold current conditions going forward(i.e. take last soil moisture readings and apply as thresholds).

A show current status mode for the interrupt controller 11 defaults towhen no keypad entry has occurred for a minute or so and shows zone byzone-threshold, last soil moisture data, irrigation is being attempted,and if irrigation is being interrupted.

The save configuration allows up to six configurations to be saved,named, and recalled (for all zones thresholds, hysteresis, adaptivealgorithms on or off, etc.). This allows for summer and winter settings,etc.

A disable setting is where all zones are enabled and the system is undercontrol of the irrigation controller 11 solely, i.e. the interrupter 12allows valves 13 a and 13 b to be on at all times when the standardirrigation controller 11 schedules irrigation regardless of the soilmoisture data. This is a “safety mode” so that if there are criticalproblems, the user is not forced to reconfigure things to keep the grassfrom dying.

A bump feature allows a user to “bump” up or down all thresholds equallyat an approximately 0.5% water by volume increment (allows for quickadjustment for hot weather or other reasons), which revert to previoussettings after 1 days unless user selects to apply them permanently.

The firmware is preferably capable of detecting missing or out of rangesoil moisture and low battery conditions and display warning.

A wireless irrigation controller mode allows the irrigation interrupter12 to function as full soil moisture data driven irrigation controller11 without the use of a standard irrigation controller 11. Essentiallyall of the features of a standard irrigation controller 11 areimplemented such as scheduling irrigation times, valve run-times, etc.These scheduled events are subjected to the same “interrupt” schemes asthe irrigation interrupter 12 based on soil moisture data.

When water is applied to the soil the wireless soil sensors 21 reportthe increase in moisture content but also look at the tail off inmoisture levels when irrigation ceases. In cases of significantoverwatering, there is a sharp spike in moisture levels followed by asharp fall after irrigation ceases. This is due to the soil essentiallybeing so wet it “free drains” below the root zone (thus wasting thewater). The present invention implements algorithms to monitor this andadjust irrigation events to eliminate this wasteful practice allowingthe system to essentially configure itself over time. The wireless soilsensor 21 is preferably directly integrated with a radio andmicrocontroller. It also preferably has a sleeve that fits over thesensor that the user removes to turn it on. It also preferably has anoptional microcontroller generated clock signal to avoid having to use aseparate oscillator for the conductivity measurement. It also preferablyhas the same RF frequency the radio uses to eliminate having to use aseparate oscillator for the soil moisture measurement. It alsopreferably uses “spread spectrum oscillators” to achieve FCC compliance.It also preferably has sensor components that are currently PCB may bemade out of conducting plastic formulations simplifying assembly,improving aesthetics, and reducing costs.

As shown in FIG. 22, the sensor apparatus 120 preferable includes adigital signal processor 135 connected to a moisture circuit 122 and asalinity circuit 123, which are both connected to a probe structure 121.The probe structure 121 is placed in the soil which is to be measured.The probe structure 121 forms an effective coaxial capacitor within thesoil. Such probe structures are well known in the art, and typicallyinclude a base and elongated conductors extending from the base anddisposed around a central elongated conductor. The digital signalprocessor 135 or microprocessor, facilitates the process, allowing formultiple conducting structures to be inserted into the soil (or othermedia of interest) as well as cabling to provide power and transfermeasurement results to recording or control instrumentation. The probestructure 121, which when placed in soil forms, electrically, thecircuit elements C_(S) and R_(s), and are referred to as forming a“capacitor.” The probe structure 121 can be arranged in a variety ofdifferent geometries many of which are shown in U.S. Pat. Nos.2,870,404, 4,288,742, and 4,540,936, all of which are herebyincorporated by reference in their entireties. The conducting structuresof the afore-mentioned '104 patent can also be included in the probestructure 121. The probe structure 121 can be made of metal, printedcircuit board, or other electrically conductive materials. Depending onthe media of interest, the range of expected C_(S) and R_(s) to bemeasured and frequencies employed, many different geometries and sizescan be employed as the probe structure 121 in sensor.

FIG. 23 illustrates a graph 302 showing a calibration curve of thevariation in 1/RC (X axis) with increasing sample conductivity (Y axis).

FIG. 24 is an embodiment of sensor 21. The wireless sub-surface sensor21 preferably has a housing 30, a processor 31, a configurationswitchable antenna 32, an antenna circuit 39, sensors 33 a and 33 c, anda power supply 34. At least one of the sensors 33 are preferablymeasures the electrical properties of the soil. The antenna circuit 39tunes the antenna to optimize the transmission. The antenna circuit 39preferably comprises a plurality of resistors and inductors for tuningthe antenna to match an optimal impedance for transmission.

From the foregoing it is believed that those skilled in the pertinentart will recognize the meritorious advancement of this invention andwill readily understand that while the present invention has beendescribed in association with a preferred embodiment thereof, and otherembodiments illustrated in the accompanying drawings, numerous changesmodification and substitutions of equivalents may be made thereinwithout departing from the spirit and scope of this invention which isintended to be unlimited by the foregoing except as may appear in thefollowing appended claim. Therefore, the embodiments of the invention inwhich an exclusive property or privilege is claimed are defined in thefollowing appended claims.

1. A wireless sub-surface soil sensor comprising: a microcontrollerconfigured to measure analog voltages and perform calculations todetermine the real-time soil conductivity value and the real-time soildielectric constant value; an antenna; and an antenna circuit incommunication with the microcontroller and the antenna, the antennacircuit comprising a plurality of resistors and inductors for tuning theantenna, the antenna circuit configured to utilize a real-time soilconductivity value of a soil area and a real-time soil dielectricconstant value of a soil area to vary the properties of the antenna toclosely match the soil conditions and improve a communication range andcommunication reliability of the antenna to wirelessly transmit aplurality of soil data through the soil to the surface.
 2. A wirelesssub-surface soil sensor comprising: a microcontroller configured tomeasure analog voltages and perform calculations to determine thereal-time soil conductivity value and the real-time soil dielectricconstant value; an antenna; a probe conducting structure to be placed inthe material forming a capacitor connected to a soil moisture circuit; asoil moisture circuit comprising a high frequency oscillator forapplying electrical stimulus to the probe structure, a known referencecapacitor connected in series to the high frequency oscillator, and afirst voltage meter located between the high frequency oscillator andthe reference capacitor; a soil salinity circuit comprising a lowfrequency oscillator for applying electrical stimulus to the probestructure, a known reference resistor connected in series to the lowfrequency oscillator, and a second voltage meter located between the lowfrequency oscillator and the reference resistor; wherein the respectivecircuits connect between the reference capacitor and the referenceresistor, at which point the circuits are connected to the probestructure and a third voltage meter; and an antenna circuit incommunication with the microcontroller, the antenna circuit comprising aplurality of resistors and inductors for tuning the antenna, the antennacircuit configured to utilize a real-time soil conductivity value and areal-time soil dielectric constant value to vary the properties of anantenna to closely match the soil conditions and improve a communicationrange and communication reliability of the antenna to wirelesslytransmit a plurality of soil data through the soil to the surface.
 3. Amethod for tuning an antenna of a wireless sub-surface sensor positionedin a soil area, the method comprising: determining at least onereal-time electrical property of a soil area; analyzing the at least onereal-time electrical property to determine an optimal antenna propertyfor efficient transmission and range; tuning an antenna of a wirelesssub-surface sensor with an antenna circuit of the wireless sub-surfacesensor, the antenna circuit configured to utilize the at least onereal-time electrical property to tune the antenna to the optimal antennaproperty for efficient transmission and range to create a tuned antenna,the wireless sub-surface antenna buried below the surface in the soil;and transmitting soil data in a wireless communication from the tunedantenna through the soil to a receiver above ground.
 4. The methodaccording to claim 3 wherein the plurality of soil electrical propertiescomprises soil conductivity and soil dielectric constant.